Fair Value of Financial Instruments - Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 27, 2013	Apr. 28, 2013	Oct. 28, 2012
Low Duration Bond Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	$ 2,060	$ 2,076	$ 2,065
Limited Term Bond Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	2,561	2,092	2,073
Intermediate Term Bond Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	1,599	1,118	1,103
Quoted prices in active markets for identical assets - Level 1 [Member] | Low Duration Bond Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	2,060	2,076	2,065
Quoted prices in active markets for identical assets - Level 1 [Member] | Limited Term Bond Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	2,561	2,092	2,073
Quoted prices in active markets for identical assets - Level 1 [Member] | Intermediate Term Bond Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	$ 1,599	$ 1,118	$ 1,103